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28 June 2009, Volume 16 Issue 2 Previous Issue    Next Issue
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Review or Special Topic

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Genetics and Improvement of Bacterial Blight Resistance of Hybrid Rice in China ZHANG Qi 2009, 16(2): 83-92 .  DOI: 10.1016/S1672-6308(08)60062-1 Abstract ( )   PDF   Since 1980s, rice breeding for resistance to bacterial blight has been rapidly progressing in China. The gene Xa4 was mainly used in three-line indica hybrid and two-line hybrid rice. The disease has been ‘quiet’ for 20 years in China, yet in recent years it has gradually emerged and been prevalent in fields planted with newly released rice varieties in the Changjiang River valley. Under the circumstances, scientists inevitably raised several questions: what causes the resurgence and what should we do next? And/or is resistance breeding still one of the main objectives in rice improvement? Which approach do we take on resistance breeding so that the resistance will be more durable, and the resistance gene will be used more efficiently? A combined strategy involving traditional method, molecular marker-assisted selection, and transgenic technology should bring a new era to the bacterial blight resistance hybrid rice breeding program. This review also briefly discusses and deliberates on issues related to the broadening of bacterial blight resistance, and suitable utilization of resistance genes, alternate planting of available resistance genes; and understands the virulent populations of the bacterial pathogen in China even in Asia.

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Mapping a Rice Glabrous Gene Using Simple Sequence Repeat Markers WANG Dong, SUN Shu-xia, GAO Fang-yuan, LU Xian-jun, LI Zhi-hua, REN Guang-jun 2009, 16(2): 93-98 .  DOI: 10.1016/S1672-6308(08)60063-3 Abstract ( )   PDF   Inheritance analysis and gene mapping of the glabrous trait were conducted using the crosses between a pubescent rice material Chuanxiang 29B (an aromatic elite maintainer line of hybrid rice), and two glabrous rice materials, Lemont and R2 (R2 is a new restorer line of hybrid rice). All F1 plants from the two crosses had pubescent leaves, confirming that the pubescence trait in Chuanxiang 29B is dominant over the glabrous trait. In F2 individuals, the segregation ratio of three pubescent to one glabrous plant suggests that a single glabrous gene was present in Lemont and R2. Using the bulked segregant analysis, the linkage analysis of the simple sequence repeat markers showed that the glabrous gene, gl-1, was flanked by GL311 and GL8 with the genetic distances of 0.19 and 0.92 cM on chromosome 5, respectively.

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Relationship Between Resistance Gene Analogue and Blast Resistance in Rice CHEN Yu-min, FAN Cheng-ming, YANG Yan, HE Yue-qiu, 2009, 16(2): 99-105 .  DOI: 10.1016/S1672-6308(08)60064-5 Abstract ( )   PDF   DNA fragments of 43 rice varieties were amplified with 11 pairs of primers designed based on resistance gene analogue (RGA) of plants, and the blast resistance of the varieties was identified by inoculation with 33 isolates of Magnaporthe grisea collected from Yunnan Province, China. Clustering results revealed a significant correlation between the blast resistance and DNA bands with a correlation coefficient of 0.6117 (α=0.01), indicating that the resistance analysis based on RGA-PCR clustering analysis coincided with that based on inoculation. The correlation coefficients, ranging from 0.1701 to 0.535, however, depended on the primers. Five pairs of primers, S1/AS3, S1 INV/S2 INV, XLRR For/XLRR Rev, Pto-Kin1 IN/Pto-Kin2 IN, and NLRR For/NLRR Rev might be applied for blast resistance identification in consideration of their band numbers and polymorphisms, and their correlation coefficients with blast resistance were 0.5305, 0.4898, 0.4059, 0.3719 and 0.3524, respectively. Besides, indica and japonica rice except two highly susceptible varieties, CO39 and Lijiangxintuanheigu, could be well classified by the 11 pairs of primers.

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A Cleaved Amplified Polymorphic Sequence Marker to Detect Variation in Wx Locus Conditioning Translucent Endosperm in Rice CHEN Tao, ZHANG Ya-dong, ZHAO Ling, ZHU Zhen, LIN Jing, ZHANG Suo-bing, WANG Cai-lin 2009, 16(2): 106-110 .  DOI: 10.1016/S1672-6308(08)60065-7 Abstract ( )   PDF   The translucent endosperm trait in a japonica rice variety ‘Kantou 194’ is controlled by a Wx-mq gene which is allelic to Wx locus by genetic analysis and allelic test. The amylose content analysis showed that an intermediate amylose content between those of glutinous and non-glutinous rice existed in endosperm of homozygous Wx-mq genotype. The slight changes of amylose content in different varieties and F1 grains with an identical Wx-mq genotype might be influenced by dissimilar genetic background. To identify the Wx-mq genotype simply and rapidly, a cleaved amplified polymorphic sequence (CAPS) marker was designed. The result from the molecular detection indicated that it could be used for marker-assisted selection for low amylose content varieties in rice breeding.

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Developmental Genetics Analysis for Plant Height in indica Hybrid Rice Across Environments PENG Tao, ZHONG Bing-qiang, LING Ying-hua, YANG Zheng-lin, ZHA Ren-ming, XIE Rong, LIU Cheng-yuan, HE Guang-hua 2009, 16(2): 111-116 .  DOI: 10.1016/S1672-6308(08)60066-9 Abstract ( )   PDF   The developmental genetics of plant height was analyzed from two groups of three-line indica hybrid rice at two environmental conditions based on the NCII design, using the additive-dominant developmental genetics models and the statistic methods. The results showed that the rice genotypes and environmental conditions could both affect plant height, and the effects of environment on plant height decreased gradually with plant development. Additive and dominant effects both governed the performance of plant height at all developmental stages. However, the degrees of effect varied among the rice genotypes. Moreover, the interaction between environments and genotypes also affected plant height. The genetic effects differed at most developmental stages. Furthermore, the expression of additive effect was more active than that of dominant effect. Conditional interaction effects with environment also influenced plant height during genetic development, especially at the early stage. Mid-parent heterosis (HMP) increased gradually with the developmental stage of plant height, and maximized at the latest stage, whereas the heterosis over the better parent (HBP) showed small differences among the genotypes, and kept stable at the later stage, with positive numeric value. At most developmental stages, conditional HMP was positively significant, while conditional HBP was negatively significant. All above results suggest that HMP and HBP have some new expressions in all developmental periods and the levels and directions are quite different.

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Metabolome Comparison of Transgenic and Non-transgenic Rice by Statistical Analysis of FTIR and NMR Spectra Keykhosrow KEYMANESH, Mohammad Hassan DARVISHI, Soroush SARDARI 2009, 16(2): 119-123 .  DOI: 10.1016/S1672-6308(08)60067-0 Abstract ( )   PDF   Modern biotechnology, based on recombinant DNA techniques, has made it possible to introduce new traits with great potential for crop improvement. However, concerns about unintended effects of gene transformation that possibly threaten environment or consumer health have persuaded scientists to set up pre-release tests on genetically modified organisms. Assessment of ‘substantial equivalence’ concept that established by comparison of genetically modified organism with a comparator with a history of safe use could be the first step of a comprehensive risk assessment. Metabolite level is the richest in performance of changes which stem from genetic or environmental factors. Since assessment of all metabolites in detail is very costly and practically impossible, statistical evaluation of processed data of grain spectroscopic values could be a time and cost effective substitution for complex chemical analysis. To investigate the ability of multivariate statistical techniques in comparison of metabolomes as well as testing a method for such comparisons with available tools, a transgenic rice in combination with its traditionally bred parent were used as test material, and the discriminant analysis were applied as supervised method and principal component analysis as unsupervised classification method on the processed data which were extracted from Fourier transform infrared spectroscopy and nuclear magnetic resonance spectral data of powdered rice and rice extraction and barley grain samples, of which the latter was considered as control. The results confirmed the capability of statistics, even with initial data processing applications in metabolome studies. Meanwhile, this study confirms that the supervised method results in more distinctive results.

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Observation on Double Fertilization and Early Embryonic Development in Autotetraploid Polyembryonic Rice DAI Xi-mei, YANG Xu, HUANG Qun-ce, QIN Guang-yong 2009, 16(2): 124-130 .  DOI: 10.1016/S1672-6308(08)60068-2 Abstract ( )   PDF   The process of double fertilization and the characters of embryo and endosperm development in an autotetraploid polyembryonic mutant rice IR36-Shuang were studied with a laser scanning confocal microscopy. Some abnormalities including degenerated ovary, abortive embryo sac, single fertilization, double-ovule and double-embryo and so on. were found during double fertilization and embryo development in IR36-Shuang. The rate of the abnormalities was 46.67% in IR36-Shuang, significantly higher than that in the control, an autotetraploid rice line IR36-4X (33.00%). Cytological and embryonic evidences were provided for seed setting decline and the initiation of additional embryo in IR36-Shuang.

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Division of Free Nuclei in Rice Endosperm and Its Influencing Factors LIU Man-xi, WANG Zhong, WU Xiao-mei, CHEN Yi-fang, GU Yun-jie 2009, 16(2): 131-137 .  DOI: 10.1016/S1672-6308(08)60069-4 Abstract ( )   PDF   The division process of endosperm in rice and its influencing factors were investigated. Total dissection, resin embedding and sectioning under light and transmission electron microscopes were used to observe the division patterns of free nuclei and cytological characters of an endosperm. The various division patterns of free nuclei in rice endosperm included mitosis, amitosis, and the mitosis to amitosis change without an interphase. The division velocity of free nuclei in rice endosperm varied with the internucleus distance. Comparing to a cluster, the division velocity increased when the free nuclei were separated from each other. Moderately higher temperatures also enhanced the proliferation and shortened the division cycle of free nuclei in rice endosperm. To a certain extent, nitrogenous fertilizer applied at the booting stage together with a moderate drought treatment accelerated the division of free nuclei as well.

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Effects of Plant Density and Nitrogen Application Rate on Grain Yield and Nitrogen Uptake of Super Hybrid Rice LIN Xian-qing, ZHU De-feng, CHEN Hui-zhe, ZHANG Yu-ping 2009, 16(2): 138-142 .  DOI: 10.1016/S1672-6308(08)60070-0 Abstract ( )   PDF   The nitrogen uptake, yield and its components for two super-high-yielding hybrid rice combinations, Guodao 6 and Eryou 7954 were investigated under different plant densities (15, 18, and 21 plants/m2) and different nitrogen application rates (120, 150, 180, and 210 kg/hm2). The experiment was conducted on loam soil during 2004–2006 at the experimental farm of the China National Rice Research Institute in Hangzhou, China. In these years, the two hybrid rice clearly showed higher yield at a plant density of 15 plants/m2 with a nitrogen application rate of 180 kg/hm2. Guodao 6 produced an average grain yield of 10 215.6 kg/hm2 across the three years, while the yield of Eryou 7954 was 9 633.0 kg/hm2. With fewer plants per unit-area and larger plants in the plots, the two hybrid rice produced more panicles per plant in three years. The highest nitrogen uptake of the two hybrid rice was at a plant density of 15 plants/m2 with a nitrogen application rate of 180 kg/hm2. Further increasing nitrogen application rate was not advantageous for nitrogen uptake in super-high-yielding rice under the same plant density.

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Genotypic Differences in Growth and Physiological Responses to Transplanting and Direct Seeding Cultivation in Rice CHEN Song, CAI Sheng-guan, CHEN Xin, ZHANG Guo-ping 2009, 16(2): 143-150 .  DOI: 10.1016/S1672-6308(08)60071-2 Abstract ( )   PDF   The field experiments were conducted to investigate the growth and physiological responses of six super hybrid rice combinations to two planting methods, transplanting (TP) and direct seeding (DS) during 2006–2007 and 2007–2008. The 1000-grain weight and number of tillers per plant at the early growth stage, the maximum quantum yield of PSII (Fv/Fm) and transpiration rate (Tr) were higher in DS plants than in TP ones, whereas the grain yield, number of panicles per square meter, seed setting rate, net photosynthetic rate (Pn) and stomatal conductance were lower in DS plants. However, little difference was detected in number of grains per panicle, stem (shoot) and leaf weight between the combinations in the two planting methods. The responses of plant growth and physiological traits to planting method differed greatly among the six combinations. In both planting methods, Chouyou 58 and Yongyou 6 had the highest and lowest panicle biomass and Pn, respectively. The higher yield of Chunyou 58 was associated with more numbers of panicles per square meter and grains per panicle in both planting methods. The results indicate that lower grain yield in DS relative to TP is attributed to more excessive tillers at the early stage, lower leaf biomass and photosynthetic rate at the late stage.

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Influences of Cadmium on Grain Mineral Nutrient Contents of Two Rice Genotypes Differing in Grain Cadmium Accumulation Cheng Wang-da, Yao Hai-gen, Zhang Hong-mei, Tao Xian-guo 2009, 16(2): 151-156 .  DOI: 10.1016/S1672-6308(08)60072-4 Abstract ( )   PDF   A pot experiment was conducted to study the effects of Cd on grain Cd, K, P, Mg, Zn, Cu, Pb, Fe and Mn accumulation in two rice genotypes (Xiushui 63 and Xiushui 217) differing in grain Cd accumulation under four Cd levels, i.e. 0, 0.5, 2.5 and 12.5 mg/kg. Rice genotype greatly affected the grain K content, but not significantly for P, Mg, Zn, Cu, Pb, Fe and Mn contents. There were remarkable effects of additional Cd on the contents of P, Mg and Zn in grains, while not significant for K, Cu, Pb, Fe and Mn contents. No significant differences were found in the interaction of genotype by additional Cd on these nine element contents. The low grain Cd accumulation genotype Xiushui 217 had significantly higher grain K, Mg, Cu and Mn contents than the high grain Cd accumulation genotype Xiushui 63, but the case was opposite for Zn, Pb and Fe contents. It also showed that Cd addition levels significantly influenced the K, P, Mg, Zn, Cu, Pb, Fe and Mn contents in rice grains. Grain K, P, Mg, Zn, Fe and Mn contents reduced with the increasing rate of Cd addition.

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Real-time Fluorescence PCR Method for Detection of Burkholderia glumae from Rice FANG Yuan, XU Li-hui, TIAN Wen-xiao, HUAI Yan, YU Shan-hong, LOU Miao-miao, XIE Guan-lin 2009, 16(2): 157-160 .  DOI: 10.1016/S1672-6308(08)60073-6 Abstract ( )   PDF   Burkholderia glumae causing seedling rot and grain rot of rice was listed as a plant quarantine disease of China in 2007. It’s quite necessary to set up effective detection methods for the pathogen to manage further dispersal of this disease. The present study combined the real-time PCR method with classical PCR to increase the detecting efficiency, and to develop an accurate, rapid and sensitive method to detect the pathogen in the seed quarantine for effective management of the disease. The results showed that all the tested strains of B. glumae produced about 139 bp specific fragments by the real-time PCR and the general PCR methods, while others showed negative PCR result. The bacteria could be detected at the concentrations of 1×104 CFU/mL by general PCR method and at the concentrations below 100 CFU/mL by real-time fluorescence PCR method. B. glumae could be detected when the inoculated and healthy seeds were mixed with a proportion of 1:100.

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Effects of Chalkiness on Cooking, Eating and Nutritional Qualities of Rice in Two indica Varieties Liu Qi-hua, Zhou Xue-biao, Yang Lian-qun, Li Tian 2009, 16(2): 161-164 .  DOI: 10.1016/S1672-6308(08)60074-8 Abstract ( )   PDF   An experiment was conducted to investigate the effects of chalkiness on cooking, eating and nutrition qualities of rice using Gangyou 527 (indica hybrid rice) and Zhaiyeqing 8 (conventional indica rice) as materials. Compared with the milled rice without chalkiness, amylose content, final viscosity, setback and consistence increased significantly, while gel consistence, peak viscosity and breakdown decreased remarkably and other RVA values did not have significant changes in the chalky rice of Gangyou 527. The differences in the above indices between the chalky and non-chalky rice was not remarkable in Zhaiyeqing 8. The crude protein content of chalky rice in Zhaiyeqing 8 was significantly lower than that of non-chalky rice, but there was no remarkable change between the chalky and non-chalky rice in Gangyou 527. Glutelin content fell significantly, and albumin, globulin, prolamine and lysine contents did not change significantly in chalky rice compared with non-chalky rice in the two varieties.